Dissector tube



April z5, 195o RE E wm I R O m Mm Bm.

Original Filed Aug. 26. 1947 Nm. bhhhvm. mm.

Nm. om.

/N VEN TOR M. OUVER 47( Mfg l By ATTORNEY Patented Apr. 25, 1950 UNITED DISSECTOR TUBE Bernard M. Oliver, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York 3 Claims. (Cl. Z50-155) This invention relates to electron camera tubes and more specifically to electron camera tubes of the dissector type. This application is a division of application Serial No. 770,639, filed August 26, 1947.

It is an object of this invention to reduce certain distortions heretofore generally produced in television transmitter tubes of the dissector type.

One well-known form of cathode ray television pick-up device is called the dissector. In the usual dissector tube, an image of the object is formed on a photoelectric cathode, thereby giving rise to a stream of electrons various elemental portions of a cross-section of which, taken at a plane containing a scanning aperture in front of a pick-up electrode, correspond respectively to the elemental areas of the optical image on the cathode. The electrons are accelerated towards the scanning aperture by an axial electrostatic eld. In order to use the tube as a television pick-up device, three independently variable magnetic elds are usually necessary. First, an axial magnetic field is required to form an electron image at the end of the tube remote from the photocathode. Next, two transverse magnetic fields, known as the horizontal and vertical deilecting (or sweep) fields, are required in order to deflect the electron stream from side to side and up and down and thus displace the electron image in these directions. By means of these two transverse magnetic fields, it is possible to move all elemental parts of the electron image in succession over a fixed aperture located in the image or scanning plane. The number of electrons received by an electrode directly behind the aperture depends on the electron density of that prtion of the electron image which falls on the aperture, and hence in turn is proportional to the light intensity falling on the corresponding element of the cathode surface. In certain special applications, such as those in which the material to be scanned is a moving nlm, one deecting field is not necessary. In television systems employing the usual dissector tube as a pick-up device, it has been noted that the picture produced on the screen of the receiving tube has been distorted due, at least in part, to the fact that the magnetic sweep coils and, in some cases, the focussing coil and also the electrode structure producing the electrostatic eld in the dissector have been so formed as to produce non-uniform fields.

It has been found that the geometric distortions produced in the dissector type tube can be greatly minimized by using substantially uniform accelerating, focussing and deflecting elds. The

present invention relates primarily to electron optical arrangements for producing substantially uniform accelerating elds.

In an illustrative embodiment of the invention, there is provided a dissector tube`having a multiplicity of accelerating rings therein which arc placed at progressively higher potentials in the direction of electron movement. Preferably, at least one ring is on the side of the anode remote from the cathode and at least one ring is on the side of the cathode remote from the anode. A metal cap, of mesh material for example, is l0- cated at the anode end of the tube. A substantially uniform electric field throughout the useful volume of the dissector is produced by this elec` trode arrangement.

The invention will be more readily understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof in which:

Fig. 1 is an enlarged elevation View, with portions broken away, of the dissector tube of this invention together with its associated sweep and focussing windings; and

Fig. 2 is a circuit diagram of Voltage divider circuits, including vacuum tubes, suitable for use with the tube of Fig. 1 to produce the necessary voltage on various elements therein.

Referring more specifically to the drawing, Fig. 1 shows, by way of example for purposes of illustration, a dissector tube I0 (with portions broken away) and associated horizontal sweep winding II, vertical sweep winding I2 and focussing winding I3, which windings are preferablyv formed and Wound in the manner shown in Fig.. 7 of B. M. Oliver Patent 2,278,478, issued April 7,v 1942, so that a substantially uniform magnetic eld is produced within the space enclosed by the dissector I 0. To assist in the production of a uniform magnetic focussing field, particularly at the ends of the dissector, additional end turns I4 and I5, the purpose of which is well understood by the workers in the art, have been added at the ends of the focussing winding I3. The windings II, I2 and I3 are supported on suitable forms IE, I'I and I8, respectively, and the various windings are shielded by means of cylindrical electrostatic shields.

The dissector tube I0 comprises a photoelectric cathode 22 upon which radiations from an ob ject O are focussed by any suitable optical system represented schematically by the single lens 38, an electrostatic accelerating field producing means comprising a plurality of conducting rings .23 to 37, inclusive, and a pick-up member 39 at .-sistor are connected to a transmitter Aoutputsignals of the dissector le 'arepreparedifor the end of the tube lil remote from the photoelectric cathode 22. The pick-up member 39, as in the usual dissector tube, preferably comprises a metallic iinger having an aperture therein of elemental size and an anode back of the aperture for receiving electrons which pass through it. Any suitable electronmultiplier (not shown) may be enclosed within the pick-up member 39. In order that the electric eld, which accelerates the photoelectrons from the cathode 22 towards the anode in the member 39, be uniform in intensity and axial in direction, the conducting ringsv23-to 31, inclusive, are connected'respectively-to points of dierent potential on the voltage divider 43 which is shown in detail in Fig. 2. The divider 43, the circuit arrangement of which will'bede'scribed more fully below, is so arranged that'the potential applied to each of the rings 23 to 3l, inclusive, increases uniformly in the direction of theel'ectron flow. A mesh cap 44 on or near the end wall of the tube it is placed at the same .potential as v'the .ring 23. The metallic nger 39 is rplaced yat ground potential which isalsothe potential voi the vnearest ring member 25. The anode in theapickup -nnger 39 is 'connected ythrough a resistor v(not shown) to ground and the terminals of-this re wherein the radiation, by means of anysuitable sending antenna, to a receiving station.

Sweep waves are 'applied to Ithehorizontal and kvertical sweep windings, fand alternating cornponents applied to the various Vpotential rings @2% to 3l, inclusive, in the dissector "tube lil -invany suitable manner, as, Alfor example, in the man'- ner disclosed in the `parent application, :Serial No. 770,639.

The voltage vrdivider circuit shown inFig..-2 lis suitable yfor .producing 4the ipotentials required for the tube of Fig.1. yThe :circuit of Fig. VZilla-s a negative part (comprising vthe vtwo ltubes t5! ,and E52 on the vleft and the circuits :associated therewith) and a positive .part (the-rest of fthe circuit). The pick-up ngerg andthe :ring nearest it are connected to ground which is'the Vpotential of the terminal common lto the 'left Vand 'right .parts vol :the circuit f. :IA high voltage, direct current power-'supply 'lill having lits positive terminal 'grounded ris associated "with the 'positive partici 'the vacuum tube .potentioma -e'ter circuit shown in Fig. 2. Between .ground :and Athe lnegative 'terminal Aoftlr-i power suppl-y itil are connected Vin series a resistor it?, land the anode-cathode rcircuits of a numberioivacuum tubes lidi? to i123, inclusive. .The `varnode'oi tube iii@ -is Vconnectedto. ground and -eac'h of thek tubes Hd to ld, inclusive, yhas its anode corrnecte'd to the cathodesof `ithe preceding tube. The Ycathode ior tube i2@ is connected through resistor ifi@ `to .the negative yterminal fof *thepower supply i8?. As a result, Ythe y'anode'- cathode .paths of the tubes iilto flLiinCluSiK/Ye, are all in series and '-ii vnocurrent*isxdurawn vby the of t'nese tubes or iro'm Yany oi the -terh murals of these tubes shown. connected Fig. 2 to rings tte el, inclusivethe saine.platecurn rent flow in Eall the tubes.

The grid of each of the tubes 39 to ldnelusive, is connected to'tlie corresponding junction point between apairof the .resistors aldil fito ifi-i3, inclusive, which resistors .are conneoted1in series between ground and the :negative Iterminal of the high voltage supply. `As fa result i"each grid or" the'seriesof tubes its Ito l, inclusive,

--inclusi-ve, form a set of potentials decreasing :progressively ziromground (potential of ring 2li)V tora large negatio/eA potential (potential of ring Each of the resistors l2! to $32, inclusive, is shuiated"by'fa capacitor i3d to M5, respecf't'ively. 'The electric eld formed by these ring voltages is extended beyond the cathode 22 by mea-ns \oi the ring 3l which is more negative than the cathode 22 and extended in the opposite vdirection bey'ond the .piclreu-p ringer 3S by meansofzthe Arings 12d land it to which are api 4plied .positive :potentials with respect to tlfiatvlf the anode nger 39 .by means of ther-left portion of the voltage divider circuit i3 shownin Fig.V 2. .The ineen cap lon or ffnea'r fthe end `wall "of Vthe tube fis placed `Vat the same potential Yas .the ring and is Vusedfto preverit vthe electric field lines trom cur-ving up vtoward-'the ring 23. This .makesfpossible 'a inor'e uniform eld distribution within the tube it.

Referring .now ytothe left -lportion ofithe volt age vdivider 'circuit loi Fig. :2, 'the `potentionie't'er comprising the resistors Ellie, WE Iand idd' is oonnected fbetween the plus terminal foi -a direct currentsupply .i-zl designated "fDls'sector voltage supply #2 (which iis 'usually of lower voltage than 'the Dissect'or voltage supply `#1") and ground. The resistors VTIi land 'Hi8 @are respectively 'sliuntedbycondensers MSE and les. Tire terminal Itri-iis connected Ito Ythe oommonlterininal or .resistors Vvist* and 'fiel aridlto the grids'ofia tube 52, 'the anode-'cathode 'ci'rcudtY of :which -lis connected in Sa kseries fcircuit "with the 'corresponding circuitof atube T52 an'dlafresis'tor l5?, across vthis power supply iid?. "-The common terminal of ith'e uresistors fi'l' and ll'i is lconnected to the :control 'element fof the tube J52.

Thecatliodes of ythe tubes lidi and 1552 Eare ree' spectivel-y connected ito thermes-23 and In th'e arrangement of Fig `2, yi-t ywill be noted that use is madeof ia cathode follower iccnn'ec tion kto remove Aoutinit voltages. This has the ei'ect of decreasing'the impedance v-as seen by the k.rings "of fthe ydissector "tube i'i. CurrentsV drawnlby these `Jringsin Lth'e l'disseetor Ytherefore haveflittle effect on rthe 3'potentials foi the rings.

The-'operation of the system shown iin and f2 'Twill now be described. image ci fthe objectfO is focussed-upon the -photoelectric cath-- ode liii-'E -bymeans-'of thellenssystem sra'ndrphotoelectrons 'emitted from -this cathode fare formed into -a Vbeffirn havingbrbss-seotioral area 'con responding to that oi `1the optical image. The potentials applied to vthe rings 1F53 %o 135, iinclusive, are sufficiently l'arge to produce saturated photo-emission 'fromfthe cathode 123;. For eX- ample, `'tl'leiring ist Vineare''st-the 'rin'g'di at `'cathode potential is placed-fat la potential of about 'i60 volts positive with"respect to the cathode'an'd the following `rings -liave 'progressivelylarger `pon tentials fap'pli'ed `lthereto, the diierence between every -vtwo successive rings being 'approaimatelyspaced along the axis of the tube, a substantially uniform axial electric eld throughout the volume of the dissector is produced if the potential diierence between adjacent rings is the same in all cases, and provided the cathode 22 and mesh cap 4A are respectively placed at the potentials of the rings having the same axial position. The potentiometer circuit of Fig. 2 and the construction of the tube I@ are such as to permit these conditions to be met.

The uniform axial iield set up by the focussing coil I3 in cooperation with the substantially uniform electric field produced by the potentials applied to the conducting rings 23 to 31, inclusive, and to the cathode 22 and mesh cap 44, bring the photoelectrons to a focus in the plane of the aperture in the pick-up member 39, thus forming an electron image of the object in this plane. 'I'he horizontal and Vertical sweep coils I I and I2 produce magnetic elds uniform in intensity throughout the dissector volume and in directions transverse to the axis of the dissector. Each field, which is continuously varying with time due to the saw-toothed current applied to the coils, sweeps the entire electron image across the aperture of the pick-up member 39, thereby allowing successive elements in the electron image to pass through the aperture. The output of the pick-up member 39 is amplified and prepared for transmission over the antenna in a manner well known to the workers in the television art. If a motion picture nlm is the object O, one of the sweep coils need not be used, one direction of the scanning being supplied by the motion of the film.

Various modications can be made in the various embodiments of the invention described above without departing from the spirit thereof, the scope of which is indicated in the claims.

What is claimed is:

1. A cathode ray television transmitter tube of the type containing a cathode and an anode and wherein a beam of relatively large cross-sectional area compared with the size of an elemental area of an object to be televised is formed, and means for producing an electric iield between said cathode and anode for accelerating said beam within said tube, said eld producing means comprising a plurality of rings axially spaced in the tube, at

least one of said rings being located entirely on the side of said anode remote from said cathode.

2. A cathode ray television transmitter tube of the type containing a cathode and an anode and wherein a beam of relatively large cross-sectional area compared with the size of an elemental area of an object to be televised is formed, and means for producing an electric field between said cathode and anode for accelerating said beam within said tube, said eld producing means comprising a plurality of rings axially spaced in the tube, at least one of said rings being located on the side of said cathode remote from said anode and at least one of said rings being entirely on the side of said anode remote from said cathode.

3. In combination, a cathode ray television transmitter tube of the type containing a cathode and an anode and wherein a beam of relatively large cross-sectional area compared with the size of an elemental area of an object to be televised is formed, means for producing an electric eld between said cathode and anode for accelerating said beam within said tube, said eld producing means comprising a plurality of rings axially spaced in the tube, at least one of said rings being located on the side of said cathode remote from said anode and at least one of said rings being on the side of said anode remote from said cathode, and a conducting element on the wall of the tube remote from said cathode, and means for placing said rings at potentials the average value of which increases progressively in an axial direction from the rst ring in the tube at the end nearer the cathode to the last ring in the tube near the end thereof nearer said anode, said conducting element being placed at the same potential as the last ring in the series.

BERNARD M. OLIVER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,189,319 Morton Feb. 6, 1940 2,278,478 Oliver Apr. 7, 1942 2,323,986 Flory July 13, 1943 

